Two types of arguments support a quantificational view of definite DPs. First, definite DPs share properties with other quantified expressions. In particular, they pattern together in antecedent-contained deletion constructions, they show weak crossover effects, and at least some of them interact scopally with other quantified expressions. Second, the apparent failure of (some) definite DPs to interact scopally with other quantified expressions and to exhibit island effects stems from two properties of definite DPs: they are all principal filters, and the witness set of singular definite DPs is a singleton. These two properties have the effect of rendering the wide and narrow scope readings of definite DPs indistinguishable.